Process for the production of acetylene,ethylene and aromatics

ABSTRACT

ETHYLENE, ACETYLENE, AN AROMATIC STREAM, AND PETROLEUM COKE ARE PRODUCED BY DISTILLING A CRUDE OIL TO PRODUCE LIGHT PETROLEUM ENDS, A LIGHT NAPHTH, A HEAVY NAPHTHA, AND A LESS VOLATILE REDUCED CRUDE OIL; FEEDING THE LIGHT NAPHTHA STREAM TO A HYDROCARBON PUROLYSIS FURNACE; FEEDING THE HEAVY NAPHTHA STREAM COMBINED WITH A COKER NAPHTHA TO A REFORMER WHERE SULFUR IS REMOVED, THE OLEFINS ARE SATURATED, AND THE NAPHTHENES ARE AROMATIZED, FOLLOWING WHICH AROMATICS ARE EXTRACTED FROM THE REFORMED STREAM LEAVING A MIXTURE OF NORMAL AND ISOPARAFFINS WHICH THEN ENTER THE PYROLYSIS FURNACE. THE PYROLYSIS PRODUCTS ARE SENT TO A SEPARATION TRAIN FROM   WHICH ETHYLENE AND/OR ACETYLENE ARE WITHDRAWN. OILS AND TARS ARE REMOVED FROM THE SEPARATION TRAIN AND INTRODUCED INTO A COKER, WHICH ALSO RECEIVES REDUCED CRUDE AND GAS OIL FROM THE DISTILLATION UNIT AND WHICH PRODUCES COKE, FUEL OIL, FUEL GAS, AND A COKER NAPHTHA WHICH IS COMBINED WITH THE HEAVY NAPHTHA AND FED INTO THE REFORMER.

Jan. 19, 1971 C. C. ZIMMERMAN, JR ETAL PROCESS FOR THE PRODUCTION QETYLENE, ETHYLENE AND AROMATICS 3.64 lbs.

tOOlbs v :0

LIGHT NAPHTHA y ig-gd him 25, 1969 REDUCED CRUDE AND GAS DlL 972 lbs 20 HYDROCARBON l .4 lbs 5 HEAVY 5 E NAPHTHA REFORMER FURNACE m l6.87lbs. 2 4 5 DISTILLATE FUEL 2580M 0 -0 AROMATICS COKER APHTHA 6.33 lbs.

2%? T 7.82 lbs. FUEL e GAS I 4.31 lbs. SEPARATlON TRAIN 11b8- COKER 5 Mug) 621 lbs. 5 28.67lbs.

FUEL on.

I "3 gQ' OILS AND TARS ,24 lbs.

lli/VEA/TOR CARLE c. ZIMMERMAN, JR. CHARLES F. MOSIER,JR.

United States Patent O 3,556,987 PROCESS FOR THE-PRODUCTION OF ACETYLENE,

ETHYLENE AND AROMATICS Carle C. Zimmerman, Jr., 2539 Ridge Court, Littleton,

Colo. 80120, and Charles F. Mosier, Jr., 1016 Woodside Drive, Findlay, Ohio 45840 Filed Apr. 25, 1969, Ser. No. 819,171 Int. Cl. B10g 37/10 US. Cl. 208-93 8 Claims ABSTRACT OF THE DISCLOSURE Ethylene, acetylene, an aromatic stream, and petroleum coke are produced by distilling a crude oil to produce light petroleum ends, a light naphtha, a heavy naphtha, and a less volatile reduced crude oil; feeding the light naphtha stream to a hydrocarbon pyrolysis furnace; feeding the heavy naphtha stream combined with a coker naphtha to a reformer where sulfur is removed, the olefins are saturated, and the naphthenes are aromatized, following which aromatics are extracted from the reformed stream leaving a mixture of normal and isoparaffins which then enter the pyrolysis furnace. The pyrolysis products are sent to a separation train fromwhich ethylene and/or acetylene are withdrawn. Oils and tars are removed from the separation train and introduced into a coker, which also receives reduced crude and gas oil from the distillation unit and which produces coke, fuel oil, fuel gas, and a coker naphtha which is combined with the heavy naphtha and fed into the reformer.

BACKGROUND OF THE INVENTION The prior art US. Pat. 2,143,472 to Boultbee teaches a process for catalytically reforming a naphthene feed containing olefins to obtain aromatics and parafiins. The aromatics and parafiins are passed through a separator to'separate any hydrogen produced, following which the feed is thermally cracked to obtain aromatic hydrocarbons and lowboiling olefins.

US. Pat. 3,389,075 to Addison discloses the catalytlytic reforming of a naphtha to produce aromatics and non-aromatics. Reforming is followed by fractionation, with the subsequent thermal cracking of 250 to 450 F. fractions at 1200 to 1600 F. to obtain unsaturates.

US. Pat. 3,384,570 to Kelly et a1. teaches reforming a naphtha fraction to increase the content of aromatics followed by extraction which yields a paraflinic raffinate which is cracked to obtain olefins and an aromatic extract, the aromatic extract being separately purified to obtain various aromatic products.

US. Pat. 3,389,075 to Addison discloses the catalytic reforming of a naphtha feed, the extraction of aromatics, and hydrocracking the paraflinic raflinate to obtain liquefied petroleum gases.

The above summary demonstrates that the art has not discovered the advantage of catalytically reforming coker naphthas and straight-run naphthas, then thermally cracking them in order to obtain higher yields of ethylene and/or acetylene.

UTILITY OF THE INVENTION Coker naphthas are derived from the coking of reduced crude oil. These naphthas may be used as pyrolysis feedstocks but they are inferior feeds inasmuch as their high olefin content tends to produce polymers and tars within the pyrolysis furnace. This invention upgrades both coker naphthas and heavy naphthas from crude oil distillation as pyrolysis feeds. Reforming these naphthas 3,556,987 Patented Jan. 19, 1971 saturates olefins and removes naphthenes producing a reformed stream consisting essentially of from about to about paraffins. A substantially paraflinic feed produces less polymers and tars in a pyrolysis furnace than unhydrotreated naphthas, While, at the same time, it produces greater quantities of ethylene and acetylene.

DESCRIPTION OF THE INVENTION The invention is an improved process for the operation of a hydrocarbon pyrolysis furnace consisting essentially of distilling a crude oil to produce light petroleum ends, a light paratfinic naphtha, and a heavy naphtha which is combined with a coker naphtha and fed to a reformer, wherein sulfur is removed, the olefins are saturated, and where naphthenes in the combined feeds are aromatized. Thereafter, C -C aromatics are extracted from the reformed product and the highly paraflinic ratfinate is fed into a hydrocarbon pyrolysis furnace. Acetylene and ethylene are removed from the separation unit which washes the off-gases produced by pyrolysis. Oils and tars received from the furnace are removed from the separation train and sent to the coker, which receives reduced crude and gas oil from crude oil distillation, the coker producing coke, fuel oil, gas oil, and a coker naphtha.

Paraffins and isoparaffins are prime feeds for pyrolysis, whereas olefins and naphthenes are of lesser quality, and aromatics are considered poor. The pyrolysis of olefins and naphthenes results in lower yields of acetylene and ethylene and higher yields of oils, tars and coke. Aromatics not only produce low gas yields but also very high polymer and tar yields. It is the object of this invention to obtain greater quantities of ethylene and acetylene through pyrolysis by avoiding the myriad problems which stem from the cracking of olefins, naphthenes and aromatics within the furnace.

This is achieved by reforming a combined heavy naphtha-coker naphtha stream, extracting out the aromatics, and thus producing a substantially parafiinic feed. Combining the coker naphtha with the heavy naphtha assures better control of the highly exothermic reaction which occurs when the olefins are hydrogenated in the pretreatment section of the reformer. Additionally, a valuable by-product aromatic stream is produced in the extraction step.

BRIEF DESCRIPTION OF THE DRAWING The drawing is a schematic representation of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the drawing, distillation unit 1, operating at atmospheric pressure, produces light petroleum ends boiling from about 40 to about 85 F., a light naphtha boiling in the range from about 85 to about 200 F., a heavy naphtha boiling in the range of from about 200 to about 400 F., and a reduced crude boiling at 650 F. or above. Reformer 2 consists of two sections: (1) a pre-treatment section wherein sulfur is removed from the naphtha feed stream and the olefins are hydrogenated; and, (2) a reforming section wherein the naphthenes contained in the stream are converted to aromatics. In the literature, the pre-treatment section of the reformer is sometimes referred to as a guard-case reactor.

Pressures in the pre-treatment section should range from about 350 to about 800 p.s.i.g., but a pressure in the range of from about 500 to about 800 p.s.i.g. is preferred.

675 to about 750 F. is standard for pre-treatment, but temperatures within the range of from about 700 to about 750 F. are preferred.

LOGO-4,000 standard cubic feet of hydrogen is circulated per barrel of hydrocarbon feed in pre-treatment, but a hydrogen to hydrocarbon ratio of 2,8003,000 s.c.f./ b. is preferable.

The preferred pre-treatment catalyst may be cobalt, nickel, molybdenum, or combinations thereof.

The catalyst load should be 1-10 lbs. of hydrocarbon oil per lb. of catalyst per hour, or preferably, 2-5 lbs. of hydrocarbon feed per lb. of catalyst per hour.

Following pre-treatment, reforming is carried out at pressures of from about 200 to about 700 p.s.i.g. but pressures of about 200 to about 400 p.s.i.g. are preferred.

Temperatures from about 850 to about 1,000 F. are used but temperatures in the range of from about 900 to about 950 F. are preferred.

A 3:10 mole ratio of hydrogen to hydrocarbon feed is standard but a 4:8 ratio is preferred.

Standard reforming catalysts are platinum, palladium, rubidium, ruthenium, or rhenium. Other catalysts, such as mole sieve catalysts, or the like, are also used.

Hydrocarbon Processing, 47:9 (September 1968), pp. 155-162, contains comprehensive data with respect to process descriptions, operating conditions and the economics of various reforming units currently utilized by the petroleum refining industry. However, this invention is not limited in any way to current technology be cause it can readily be adapted to improvements in the reforming art.

Extractor 3 is any conventional solvent extraction system operable with the invention. Commercial solvents such as ethylene glycol, propylene glycol, sulfur dioxide, dimethylformamide, n-methyl pyrrolidone, tetramethylene sulfone, dicyanobutene, dimethylacetamide, furfural, furfuryl alcohol, tetrahydrofurfuryl alcohol, phenol or the 4 at pressures of from 10 to about 70 p.s.i.g. but preferably operates at pressures of from 20 to p.s.i.g., and at temperatures in the range of from about 800 to about 1100" F., but preferably at temperatures of from about 850 to about 1050 F.

Having discussed the process apparatus, the drawing may now be described.

As depicted, 100 lbs. of crude oil enter distillation unit 1 through line 10. 3.64 lbs. of light petroleum ends are withdrawn from distillation unit 1 as stream G, combined with stream F, 9.72 lbs. of light naphtha, and in troduced into hydrocarbon pyrolysis furnace 4.

45.97 lbs. of reduced crude and gas oil are removed as bottoms from distillation unit 1 and fed into coker 6. 16.87 lbs. of heavy naphtha are withdrawn as stream A from distillation unit 1 and combined with 8.33 lbs. of coker naphtha removed from coker 6 as stream B; these naphthas are fed into reformer 2 which removes sulfur, saturates the olefins, and aromatizes the naphthenes in the stream, giving oif 0.42 lbs. of reformer gas overhead through line 20, and producing a reformed stream C which is fed into extractor 3 where 11.14 lbs. of C -C aromatics are extracted as stream E.

Rafiinate D is introduced into hydrocarbon pyrolysis furnace .4. The product mixture of pyrolysis is fed into separation train 5 from which 7.82 lbs. of fuel gas are removed as stream H, 4.51 lbs. of C H are removed as stream I, and 6.21 lbs. of C H are removed as stream I.

5.24 lbs. of oils and tars are removed from separation train 5 as stream K and sent to coker 6. Coker 6 produces 9.90 lbs. of coke through line 18, 28.67 lbs. of fuel oil through line 16, and 4.31 lbs. of fuel gas through line 14.

Stream compositions, all values in pounds per 100 pounds of crude oil feed, are shown in Table 1.

TABLE 1 Ole N aphfins thenes Aromatics 02H;

Oils and 2 O0 CH4 like, and/or mixtures thereof are appropriate. Two exemplary extraction systems are depicted in linear flow charts on pp. 189l90, Hydrocarbon Processing, 47:9 (September 1968).

Hydrocarbon pyrolysis furnace 4 is any suitable pyrolysis furnace referred to in Acetylene, Its Properties, Manufacture and Uses by S. A. Miller, V. I, Chapter 5, pp. 383-448; 451-471. For instance, raffinate D ma be charged to a stream cracker, produce ethylene, or, it may be thermally cracked in a Wulff furnace to produce ethylene, acetylene, or ethylene and acetylene. Any type of furnace which can be used to pyrolyze a distilled crude oil to obtain hydrocarbon gases is encompassed within the concept of the invention.

Operating temperatures for pyrolysis range from about 600 to about 3,000 E, depending upon the type of furnace used and the type of products desired. Pressures range from about 0.05 to about 50 atmospheres, but preferably should be about 0.15 to about 5 atmospheres, and most preferably, should be about 0.4 to about 2.5 atmospheres.

Separation train 5 is a standard unit known to the art where the pyrolysis gases are separated through absorption, drying, partial condensation, and/or distillation into the desired products.

Coker 6 is a, conventional delayed coker which operates MODIFICATIONS OF THE INVENTION For the sake of clarity, the invention has been described in terms of a preferred embodiment. It is not intended to limit the 1 process to the particular operation shown. Rather, all equivalents obvious to those skilled in the art are to be included within the scope of the invention as claimed.

What is claimed is:

1. In a process for treating crude oil to produce products comprising ethylene, aromatics, fuel gas and coke, by distilling said crude oil to separate as fractions, a fuel oil, a light naphtha which is fed to a hydrocarbon pyrolysis furnace, a reduced crude which is fed to a coker to produce coker naphtha, and a heavy naphtha stream, the improvement comprising combining said coker naphtha with said heavy naphtha, reforming the combined streams to form a reformed product, extracting said reformed product to remove aromatics, and feeding the rafiinate from said extraction to said hydrocarbon pyrolysis furnace together with said light naphtha, whereby there are produced ethylene and other pyrolysis products.

2. An improved process for the operation of a hydrocarbon pyrolysis furnace consisting essentially of:

(a) distilling a crude oil to separate fractions comprising light naphtha, heavy naphtha and reduced crude,

(b) coking said reduced crude to produce petroleum coke and a coker naphtha,

(c) combining said heavy naphtha from the distillation of crude oil with the coker naphtha and reforming the mixture to form a reformed product,

(d) extracting the reformed product, to form a raftinate, and an extract,

(e) feeding at least a portion of said rafiinate to said hydrocarbon pyrolysis furnace to produce products comprising ethylene, acetylene, or ethylene and acetylene.

3. The process of claim 1 wherein the light naphtha boiling from about 85 F. to about 200 F. is fed into said hydrocarbon pyrolysis furnace at a temperature of from about 600 to about 2,500 E, and a heavy naphtha stream boiling from about 200 to about 400 F. is combined with said coker naphtha boiling from about 100 F. to about 400 F. and fed into a reformer at temperatures of from about 850 to about 1,000 E, and at pressures of from about 200 to about 700 p.s.i.g.

4. The process of claim 2 wherein aromatics are extracted with a solvent selected from the group consisting of ethylene glycol, propylene glycol, tetramethylene sulfone, dimethylformamide, N-methyl pyrrolidone, sulfur dioxide, dicyanobutene, dimethylacetamide, furfural, furfuryl alcohol, tetrahydrofurfuryl alcohol, phenol, and the like, or mixtures thereof.

5. The process of claim 2 wherein the pre-treatment section of the reformer is operated at temperatures of from about 675 to about 750 F. and at pressures of from about 350 to about 800 p.s.i.g., and wherein the reformer is operated at temperatures of from about 850 to about 1,000 E, and at pressures of from about 200 to about 700 psig.

6. The process of claim 2 wherein the hydrocarbon pyrolysis furnace is operated at temperatures of from about 600 to about 3,000 P. and at pressures of from about 0.05 to about atmospheres.

7. The process of claim 2 wherein the coker is operated at temperatures of from about 800 to about 1,100 F. and at pressures of from about 10 to about psig.

8. An improved process for the operation of a hydrocarbon pyrolysis furnace consisting essentially of:

(a) distilling a crude oil to produce reduced crude and gas oils, light petroleum ends, a heavy naphtha, and a light naphtha boiling at from about F. to about 200 F.

(b) feeding said light petroleum ends and said light naphtha and a rafiinate to said hydrocarbon pyrolysis furnace at a temperature of from about 600 F. to about 3,000 P. to produce products comprising ethylene and hydrogen,

(c) coking said reduced crude and gas oils boiling at or above 650 F. at about 800 F. to about 1,100 F. to produce petroleum coke and a coker naphtha boiling from about F. to about 400 F.,

(d) combining said heavy naphtha boiling from about 200 F. to about 400 F. with said coker naphtha and introducing said naphthas into a reformer at temperatures of from about 675 F. to about 750 F.

and at pressures of from about 350 to about 800 p.s.i.g., and (e) extracting C -C aromatics from the reformed product with tetramethylene sulfone to obtain said raffinate.

References Cited UNITED STATES PATENTS 2,143,472 1/1939 Boultbee 20866 3,019,180 1/1962 Schreiner et al. 20893 3,172,840 3/1965 Paterson 208-80 3,281,350 10/1966 Codet et a1. 208-93 3,487,006 12/1969 Newman et al 208-93 HERBERT LEVINE, Primary Examiner US. Cl, X.R.

* i UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 5 5 6 9 81 Dated Jan l9 1971 C. C. Zimmerman, Jr. et al Inventor(s) It is certified that error appears in the above-identified patent and that. said Letters Patent are hereby corrected as shown below:

Col. 1, line 44: "3 ,389 ,075

to Addison" should read --2 ,43l,5l5 to Shepardson- Col. 3, line 20: "mole" should read -mol- Signed and sealed this 15th day of June 1971 (SEAL) Attest:

EDWARD M.FLETGI-IER,JR. WILLLAM E. SGHUYLER, JR. Attesting Officer Commissioner of Patents 

